I play all my games with notifications off, so achievments haven't been a big draw for me, ever. But I totally see your point, this is the only game in a LONG time where I seriously can't stop playing. I have a massive backlog of games I never finish, but Dark Souls show up and just pushes away everything else.
Notifications off: I wish there was this option for the PS3 trophies as well. Not that I reject them, but some times I really don't like them popping up and to ruin all the atmosphere that the game tried to build.